"There you are. That's what's taken over this Colony. You haven't been in touch with Control, but with these. They've used this Colony for their own ends, destroying you to live themselves!"

The Doctor reverses the gas flow causing fresh air to be pumped into the old tunnel allowing Jamie to escape. He ends up in a dance rehearsal where the guards find him. Ben reluctantly identifies him: His real personality is reasserting itself. Jamie is taking to the Pilot but the Doctor arrives and takes the Pilot, despite the Controllers protests, to see the Macra. The Pilot is horrified as Controllers voice becomes increasingly desperate ordering them to be destroyed. They are captured and locked in the pipe room with Jamie & Polly. Gas is pumped in. However Ben is now completely back to normal and frees them, causing the Macra's gas supply to be destroyed. The Tardis crew sneak away during the celebrations afterwards.

What seems to be a pretty standard "wrap it up" episode 4 punctuated by some odd inserts of colony life, needs a little bit of a closer examination especially in the light of what's gone before.

The Macra in the Control room has sort of been setup in the previous episode:

DOCTOR: Don't you see? Control are not pouring this poisonous gas into the old shaft to kill Jamie. They've quite another reason.
POLLY: Doctor, you've got to do something to help him.
DOCTOR: Before we act, we must think. Now, the Macra that have come to the surface of this planet have not found sufficient gas in the atmosphere, so they've had to get somebody to pump it up from down below.
POLLY: But if it's life and death to them, why do they waste it? Why divert it into the old shaft?
DOCTOR: That's obvious, Polly, obvious. Because there's something trapped down there they wish to keep alive.

As the Doctor indicates here:

POLLY: So that's where all the gas goes.
DOCTOR: Yes, just as I thought. These creatures would die without it.
POLLY: But how long have they been there? I mean, they weren't always in control, were they?
DOCTOR: I couldn't tell you when they were here in the first place, Polly. They're like germs in the human body. They've got into the body of this colony. They're living as parasites.
POLLY: You make it sound like a disease.
DOCTOR: Polly, that's what I think they are.
POLLY: They're in the control room. It must be like getting into the brain, mustn't it?
DOCTOR: Yes, very likely.
POLLY: Shh. They might hear you.
DOCTOR: Now then. One system must provide them with the gas they need, and the other one must be an outflow.
POLLY: Doctor, we've got to bring the Pilot here, and then we can show him these creatures really do exist.

The logic here would work a bit better though if it were Jamie that had stumbled across the control room from the old mine shaft he's trapped in and not The Doctor and Polly discovering it. In fact being able to get out of the old tunnels straight into the Colony, as Jamie does, feels a little odd and not just because he stumbles into a cheerleader rehearsal.

So lets pick a little further at what we see here. The Macra here have in all probability taken over the control room rather than built it themselves: the shape of their claws would tend to indicate they're not capable of building their own technology. They're using the control room to control the colony, we've seen them using hypnotic suggestion while people sleep earlier in the story. So how did they get up from the mines to the control room? Did they compel the humans to build it to their specifications? This would seem likely as it's sealed with the gas inside it. That in turn insinuates that the Macra themselves can control humans without the technological assistance, but we see no hint of it here. Indeed we see no hint of the Macra being intelligent or being able to speak till we see the ones in the control room: the ones in the tunnel are much more like mindless brutes.

Then there's the formula from episode 3, not mentioned again:

PILOT: Where did you find it?
DOCTOR: What?
PILOT: The formula.
DOCTOR: In my head. You know.
PILOT: Don't lie. That is a secret known only to three people in the Colony.
DOCTOR: And you're one of them, I'd say.
PILOT: Naturally. And you're not asking me to believe that in a few moments you have been able to work out a formula which it has taken our combined computers years to perfect?
DOCTOR: It does seem rather a tall order.
PILOT: Yes, of course. I know what you've done. You've broken into our secret files, haven't you?
DOCTOR: I wouldn't know how to do that. Take a look.
PILOT: Well, you must have seen the document. That's the exact computation.
DOCTOR: Really? Huh. In that case
PILOT: Do you really mean to say that you worked that out by yourself?
DOCTOR: Well, I did have a little assistance.
PILOT: Yes, I thought so. Who was it?
DOCTOR: Oh, no, no, no. Oh, no. No person. No. I simply mean that I took readings from the various dials. They appeared to be related, so I worked out the principle that controlled them. It was simple really. Like doing a sum backwards.
PILOT: Backwards?
DOCTOR: Yes. You know. Given the answer, what's the question?
PILOT: Wipe it away. Get it off there before anybody else sees it.
DOCTOR: Oh well, if you insist.

I think the problem here is that formula, which suggests something chemical, is possibly the wrong word. I suspect what the Doctor has done here is derive what's happening to the gas and where it's being pumped. It's just worded very, VERY badly.

Even if that's so there's an interesting line in there:

PILOT: Don't lie. That is a secret known only to three people in the Colony.

I think we can assume The Secret is that the Macra are in charge of the colony and are having their gas pumped out of the mine.

The Pilot is obviously one of the three people who knows the secret, as we can tell from that dialogue, but it would seem that the Macra's existence is blocked from his mind most of the time. But who are the other two people who know? My first thought was the Controller, but he died before this scene so I'd suggest that the other two are Ola and Officia, the two characters holding the keys to the locked sections. That in turn would suggest that these four are the first people to encounter the Macra.

Then at the end of this episode it's not 100% clear what's happened to the Macra: have they all been destroyed or are they merely entombed in the tunnels unable to escape without a better supply of gas?

The ending as such is very unsatisfactory: we could have done with a little more explanation instead of a few minutes of a dancing competition.

I really don't know how I feel about this story: it starts ok with an interesting premise with the colony being brainwashed as they sleep but the whole idea of a colony that seems perfect but hides a dark secret is a little derivative of writer Ian Stuart Black's first Doctor Who story The Savages. As I've explored above the wobble really sets in during episode 3 and continues into this episode which really could have done with some explanation of how the Macra took over. I definitely feel the last two episodes could have done with another pass at the scripting stage and it's possibly no coincidence that this story immediately follows The Moonbase, a tale which script editor Gerry Davis helped Kit Pedler to write. Further evidence of a need for another pass by the script editor can be found by continued references to the Macra as Insects in the script, reflecting the original intention to make them spider like, in itself an error as spiders are arachnids, which was changed when it was decided that this would be too similar to the Zarbi from the Web Planet.

The Macra return in the 3rd series of the new Doctor Who during the episode Gridlock. Reports that they come back as a result of a drunken "which rubbish Doctor Who monster can you bring back" competition between the production staff cannot be confirmed.

Incredibly in the small space of the colony we get some new characters & actors turning up this episode in the form of the Cheerleaders

Chicki is back in this episode: I'm told she's the female cheerleaders on the left in the first photo bellow. However Sandra Bryant, who played her in Episode 1, had since had a lucrative offer of work and was released to take it up so Karol Keyes plays her here, making her the first Doctor Who character, other than the title role, to be credited to two different performers. Karol Kayes in turn later works under the name Luan Peters and it's under this name that she appears in Frontier in Space: Episode Three as Sheila. She later appears in Fawlty Towers as the Australian Raylene Miles in The Psychiatrist and can be spotted as the Lady in Sports Car in the The Professionals episode Heroes.

For the record the blonde actress on the right is Jane Enshawe playing Sunaa, who also appears in episode 1 and in episode 3 where she's shown to be the Pilot's Receptionist/Secretary.

There's three Male Cheerleaders in this episode and two of them have been in Doctor Who before: Ralph Carrigan as Cheerleaders was an extra in The Myth Makers 4: Horse of Destruction, which like this episode doesn't exist. Unfortunately it's his only other unmasked Doctor Who appearance so working out which of the Cheerleaders he is is going to be a bit tough! He also appears as Monoid Two in The Ark part 3: The Return, a Robot in The Mind Robber episodes 1, 4 & 5 and a Cyberman in The Invasion episodes 6-9.

Unhelpfully the other Cheerleader is played by Terry Wright who also plays a White Robot in the same episodes of the Mind Robber so we don't know what he looks like either!

However the male Cheerleader, who we can see by himself, looks a lot like modern day photos of the third credited actor Roger Jerome so I think we can conclude that Carrigan and Wright are the two men standing behind the ladies. No idea which is which though and my usual sources on Roobarb's haven't identified them yet!

This is the only Doctor Who directing job for John Davies, a distinction shared with the director of the next story too, but he had a long career at the BBC and you can hear him interviewed in Toby Hadoke's Who's Round #62

It's also Ian Stuart Black's last script for Doctor Who: he would later novelise all three Doctor Who stories he wrote, his plus the Savages and The War Machines, for Target Books.

No episodes of the Macra Terror exist. It's the Ninth story to hold that unfortunate distinction. The previous ones are:

Marco Polo
Mission to the Unknown
Myth Makers
Massacre
Savages
Smugglers
Power of the Daleks
Highlanders

The only story with no existing episodes yet to come is The Fury From The Deep.

The Macra Terror is one of five stories to have it's soundtrack released on audio cassette in the 1990s. Colin Baker provided the narration and amongst those five stories it's the only one to retain that narration for it's later release on CD in the early 2000s. However when The Macra Terror was re-released as part of Doctor Who: The Lost TV Episodes Volume Four it featured new naration by actress Anneke Wills as well as a much better recording of the story.